I. Technical Field
The present invention relates to an inner joint member for a constant velocity universal joint, and more particularly, to an inner joint member for a constant velocity universal joint of a fixed type, which is used in a power transmission system in an automobile or various industrial machines and in which balls are used as rolling bodies, a manufacturing method therefor, and a constant velocity universal joint provided with the inner joint member.
II. Description of the Related Art
Generally, a constant velocity universal joint is provided with an outer joint member which has track grooves formed on an inner diameter side thereof, an inner joint member which has track grooves formed in an outer diameter side thereof, multiple balls which are interposed between the track grooves of the outer joint member and the track grooves of the inner joint member so as to transmit torque, and a cage which is interposed between the inner diameter surface of the outer joint member and the outer diameter surface of the inner joint member so as to hold the balls.
In the constant velocity universal joint as described above, the inner diameter surface of the outer race as the outer joint member and the outer diameter surface of an inner race as the inner joint member are brought into contact with the cage. Thus, by machining (machining of hardened steel) after a thermal curing process (quenching), the inner diameter surface and the outer diameter surface secure the dimensional accuracy and the surface roughness thereof (JP 2002-188653 A). As described in JP 2002-188653 A mentioned above, in the case of being machined after being quenched, the inner race is finished such that the surface roughness of the outer diameter surface thereof is uniform over the entire region extending from one end side of the outer diameter surface to the other end side thereof.